applications: nrf_desktop: Add release notes for Zephyr upmerge fixes

Change adds release notes for changes introduced as Zephyr upmerge
fixes. Change also slightly aligns the USB state module documentation.

Jira: NCSDK-35469

Signed-off-by: Marek Pieta <[email protected]>
Signed-off-by: Divya Pillai <[email protected]>

Author: MarekPieta

applications/nrf_desktop/doc/usb_state.rst

@@ -41,8 +41,8 @@ To select the USB stack, enable one of the following Kconfig choice options:
 
 .. note::
    The USB next stack integration is :ref:`experimental <software_maturity>`.
-   The HID boot protocol integration is not yet fully tested and may not work properly.
-   The secondary image slot background erase in :ref:`nrf_desktop_dfu` may cause missing USB HID subscriptions after a USB cable is attached.
+   For example, the HID boot protocol integration is not yet fully tested and might not work properly.
+   Because of that, the USB legacy stack is still used by default despite the fact that it is deprecated.
 
 Some of the properties are configured in the same way for both stacks, but part of the configuration is specific to the selected USB stack.
 See the following sections for details.

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -255,6 +255,13 @@ nRF Desktop
     * Application configurations to avoid using the deprecated Kconfig options :ref:`CONFIG_DESKTOP_HID_REPORT_EXPIRATION <config_desktop_app_options>` and :ref:`CONFIG_DESKTOP_HID_EVENT_QUEUE_SIZE <config_desktop_app_options>`.
       The configurations rely on Kconfig options specific to HID providers instead.
       The HID keypress queue sizes for HID consumer control (:ref:`CONFIG_DESKTOP_HID_REPORT_PROVIDER_CONSUMER_CTRL_EVENT_QUEUE_SIZE <config_desktop_app_options>`) and HID system control (:ref:`CONFIG_DESKTOP_HID_REPORT_PROVIDER_SYSTEM_CTRL_EVENT_QUEUE_SIZE <config_desktop_app_options>`) reports were decreased to ``10``.
+    * Application configurations integrating the USB legacy stack (:ref:`CONFIG_DESKTOP_USB_STACK_LEGACY <config_desktop_app_options>`) to suppress build warnings related to deprecated APIs of the USB legacy stack (:kconfig:option:`CONFIG_USB_DEVICE_STACK`).
+      The configurations enable the :kconfig:option:`CONFIG_DEPRECATION_TEST` Kconfig option to suppress the deprecation warnings.
+      The USB legacy stack is still used by default.
+    * MCUboot configurations that support serial recovery over USB CDC ACM to enable the :kconfig:option:`CONFIG_DEPRECATION_TEST` Kconfig option to suppress deprecation warnings.
+      The implementation of serial recovery over USB CDC ACM still uses the deprecated APIs of the USB legacy stack (:kconfig:option:`CONFIG_USB_DEVICE_STACK`).
+    * Configurations of the ``nrf52840dongle/nrf52840`` board target to align them after the ``bare`` variant of the board was introduced in Zephyr.
+      The application did not switch to the ``bare`` board variant to keep backwards compatibility.
 
 nRF Machine Learning (Edge Impulse)
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